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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6a16bb75db299970f4629cae151719687c2657184a0d714f7a4185b86706d27e' 
  AND token = 'iD2ZdCAwHD+cUY+Nx7NTg3ZEz2xPoMPVf0J+U0M9Kc8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}